1. Field of the Invention
The present invention relates to aspiration catheters for aspirating emboli, thrombi, and other types of particles from the vasculature of a patient, the apparatus being particularly well suited for aspiration within saphenous vein grafts, coronary arteries, and similar vessels.
2. Description of the Related Art
Human blood vessels often become occluded or completely blocked by plaque, thrombi, other deposits, emboli or other substances, which reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, or even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
Coronary heart disease is an extremely common disorder in developed countries, and is the leading cause of death in the U.S. Damage to or malfunction of the heart is caused by narrowing or blockage of the coronary arteries (atherosclerosis) that supply blood to the heart. The coronary arteries are first narrowed and may eventually be completely blocked by plaque, and may further be complicated by the formation of thrombi (blood clots) on the roughened surfaces of the plaques. Myocardial infarction can result from atherosclerosis, especially from an occlusive or near occlusive thrombi overlying or adjacent to the atherosclerotic plaque, leading to death of portions of the heart muscle. Thrombi and emboli also often result from myocardial infarction, and these clots can block the coronary arteries, or can migrate further downstream, causing additional complications.
Various types of intervention techniques have been developed which facilitate the reduction or removal of the blockage in the blood vessel, allowing increased blood flow through the vessel. One technique for treating stenosis or occlusion of a blood vessel is balloon angioplasty. A balloon catheter is inserted into the narrowed or blocked area, and the balloon is inflated to expand the constricted area. In many cases, near normal blood flow is restored. It can be difficult, however, to treat plaque deposits and thrombi in the coronary arteries, because the coronary arteries are small, which makes accessing them with commonly used catheters difficult.
Other types of intervention include atherectomy, deployment of stents, introduction of specific medication by infusion, and bypass surgery. Each of these methods are not without the risk of embolism caused by the dislodgement of the blocking material which then moves downstream. In addition, the size of the blocked vessel may limit percutaneous access to the vessel.
In coronary bypass surgery, a more costly and invasive form of intervention, a section of a vein, usually the saphenous vein taken from the leg, is used to form a connection between the aorta and the coronary artery distal to the obstruction. Over time, however, the saphenous vein graft may itself become diseased, stenosed, or occluded, similar to the bypassed vessel. Atherosclerotic plaque in saphenous vein grafts tends to be more friable and less fibrocalcific than its counterpart in native coronary arteries.
Diffusely diseased old saphenous vein grafts with friable atherosclerotic lesions and thrombi have therefore been associated with iatrogenic distal embolic debris. Balloon dilatation of saphenous vein grafts is more likely to produce symptomatic embolization than dilatation of the coronary arteries, not only because of the difference in the plaque but also because vein grafts and their atheromatous plaques are generally larger than the coronary arteries to which they are anastomosed. Once the plaque and thrombi are dislodged from the vein, they can move downstream, completely blocking another portion of the coronary artery and causing myocardial infarction. In fact, coronary embolization as a complication of balloon angioplasty of saphenous vein grafts is higher than that in balloon angioplasty of native coronary arteries. Therefore, balloon angioplasty of vein grafts is performed with the realization that involvement by friable atherosclerosis is likely and that atheroembolization represents a significant risk.
Because of these complications and high recurrence rates, old diffusely diseased saphenous vein grafts have been considered contraindications for angioplasty and atherectomy, severely limiting the options for minimally invasive treatment. However, some diffusely diseased or occluded saphenous vein grafts may be associated with acute ischemic syndromes, necessitating some form of intervention.
There is therefore a need for improved methods of treatment for occluded vessels such as saphenous vein grafts and the smaller coronary arteries which decrease the risks to the patient.
The present invention provides novel aspiration catheters for removing plaque, thrombi, emboli, and other types of obstructions from blood vessels. The present invention advantageously satisfies the need in the prior art by providing a catheter adapted to be compactly utilized in even the smaller size blood vessels. It can also be easily adapted to provide efficient and speedy evacuation in larger size vessels. This system is compatible with more common therapy devices in widespread use today, and is designed for rapid evacuation and ease of use.
The catheters of the present invention are provided in either over-the-wire or in single operator form. The catheters are sized so as to be used in very small blood vessels. Radiopaque markers are preferably incorporated into the distal ends of the catheters to facilitate their positioning within the body; similarly, a marker may be placed on the proximal end of the catheter to aid in the insertion of the catheter in to the patient. The catheters are provided with varying flexibility along the length of the shaft, such that they are soft and flexible enough to be navigated through the vasculature of a patient without causing damage, but are stiff enough to sustain the axial push required to position the catheter properly and to sustain the aspiration pressures. A support mandrel may be incorporated into the catheter to provide additional strength, A support sheath is preferably included to prevent crushing of the aspiration lumen when the catheter is used in conjunction with valves, adaptors or other fittings.
The catheters are preferably sized so as to allow the slidable insertion of a therapy catheter through the main aspiration lumen of the aspiration catheter. Alternatively, the therapy catheter can be built over the aspiration catheter. In either case, the aspiration and therapy catheters can be delivered simultaneously, saving valuable time during the procedure.
One embodiment of the aspiration catheter of the present invention therefore comprises an elongate flexible tubular body having a proximal end and a distal end. The catheter body or shaft incorporates a reinforcement such as a metallic braid or coil or a polymer coil to provide strength and flexibility to the device. A main lumen extends the length of the tubular body, and an aspiration port at the proximal end of the catheter body is in fluid communication with the main lumen, such that aspiration pressure can be provided through the port and main lumen. The distal tip on the catheter is formed of a more flexible material than that used to form the rest of the catheter shaft. Markers are preferably incorporated in to both the distal and proximal ends of the catheter to assist in positioning the catheter in the patient.
The reinforcement can be formed from a variety of materials, including polymers, stainless steel, silver or gold plated stainless steel, ELGILOY, platinum, nitinol, or a combination thereof. The distal end of the catheter body is preferably more flexible than the proximal end, and this can be achieved by providing a braid or coil density at the distal end which is greater an the braid or coil density at the proximal end. At least one support mandrel may be used to provide the catheter with additional strength.
The catheter""s main lumen is preferably sized to receive at least one separate catheter, such as a therapy catheter, which is slidably disposed herein. The inner diameter of the main lumen is preferably about 0.045.xe2x80x3
The aspiration catheter of the present invention can include a second lumen adjacent the main lumen which is adapted to receive a guidewire therethrough. The second lumen can extend substantially the entire length of the tubular body, or can extend less than 40 cm or less than 20 cm in a proximal direction from the distal end of the body. The second lumen can contain a slit through a side wall to allow insertion and removal of the guidewire therethrough. In a preferred embodiment, the second lumen has an inner diameter of approximately 0.020xe2x80x3 to receive a 0.014xe2x80x3 diameter guidewire.
The distal tip of the catheter can have at least one side port to facilitate aspiration. The distal tip can be tapered, blunt, or angled to create an oblique opening. The catheter preferably also comprises a valve in fluid communication with the main lumen, to control the application of aspiration pressure at the distal end of the device. The aspiration catheter of the present invention can also incorporate various coatings, such as hydrophilic or hydrophobic coatings, antithrombogenic coatings, or a combination thereof.
In another embodiment of the present invention, the aspiration catheter comprises an elongate flexible tubular body having a proximal end and a distal end, a main lumen extending through the tubular body sized to receive at least one separate catheter which is slidably disposed therein, an aspiration port at the proximal end of the tubular body, the aspiration port being in fluid communication with the main lumen, and a tip on the distal end of the tubular body, the tip being formed of a more flexible material than that used to form the tubular body. Again, the catheter can have a second lumen adjacent the first adapted to receive a guidewire therethrough, a specially shaped distal tip, and an optional valve in fluid communication with the main lumen.
In yet another embodiment of the present invention, the aspiration catheter comprises an elongate flexible tubular body having a proximal end and a distal end, a main aspiration lumen through the tubular body, an aspiration port on the proximal end of the tubular body in fluid communication with the main lumen, a therapeutic device attached to the distal end of the tubular body, and a tip on the distal end of the tubular body formed of a more flexible material than that used to form the tubular body itself. The therapeutic device can be an inflatable balloon and the catheter can include a separate inflation lumen for the balloon adjacent the main lumen.
The aspiration catheter may be part of an aspiration system which comprises the aspiration catheter, an extension line having a valve or stopcock to control the delivery of the aspiration pressure, and a source of negative pressure such as a syringe.
Accordingly, the catheters of the present invention provide for very fast and efficient aspiration of the working area surrounding the occlusion in a blood vessel. The catheters can be utilized in a wide range of vessel diameters, including extremely small ones, are easy to use and can quickly and efficiently evacuate occlusions and debris, allowing the physician to restore normal blood flow in these vessels in a very short period of time.